The Siemens SENTRON 5SL6306-6MB is a 3-pole miniature circuit breaker with B tripping characteristic, rated 6 A at AC and breaking 6 kA per EN 60898 and IEC 60947-2.
Ratings that matter for the panel
Rated 6 A at 30 °C ambient, the 5SL6306-6MB derates to 5.7 A at 40 °C and 5.52 A at 45 °C — a 5% and 8% drop respectively. If your enclosure runs hot near a kiln or furnace, size the load circuit accordingly. Multi-phase operation is rated at 400 V AC nominal, with a maximum of 440 V AC. The DC rating tops out at 72 V — this is an AC breaker; don't spec it for a DC bus without checking the voltage curve. Mechanical service life is 20 000 switching cycles typical.
Dimensions: 54 mm wide (3 MW), 90 mm high, 76 mm deep, with an installation depth of 70 mm behind the panel face. Mounts in any position. Halogen-free and silicon-free construction, sealable, with touch protection on the terminals.